LED technology is so cheap that now you can throw it away. So the Graffiti Research Lab has dreamed up LED Throwies, colorful little LED markers you can make yourself. They require a 10mm LED and a button-size lithium battery and are taped together with a rare earth magnet for superior stickage. Each "Throwie" costs less than a buck if you buy the ingredients in bulk. All you need is a magnetic surface and you're ready for some LED throwing. This is said to be especially fun when you toss a bunch of them onto a metal surface that's high off the ground, out of reach of interlopers who might spoil the fun. Once they're stuck up there, they stay lit for up to two weeks. It's harmless graffiti that s actually kind of pretty.